scholarly journals Depletion of the AD risk gene SORL1 selectively impairs neuronal endosomal traffic independent of amyloidogenic APP processing

2020 ◽  
Author(s):  
Allison Knupp ◽  
Swati Mishra ◽  
Refugio Martinez ◽  
Jacquelyn E. Braggin ◽  
Marcell Szabo ◽  
...  
Keyword(s):  
Late Onset ◽  
Endosomal Trafficking ◽  
Loss Of Function ◽  
App Processing ◽  
Early Endosomes ◽  
The Central Nervous System ◽  
Sorting Receptor ◽  
Induced Pluripotent ◽  
A Site ◽  
Golgi Network

SummaryThe SORL1 gene encodes for the protein SorLA, a sorting receptor involved in retromer-related endosomal traffic. Many SORL1 genetic variants increase Alzheimer’s disease (AD) risk, and rare loss-of-function truncation mutations have been found to be causal of late-onset AD. SORL1 is expressed in neurons and glia of the central nervous system and loss of SORL1 has been reported in AD tissue. To model the causal loss-of-function mutations, we used CRISPR/Cas9 technology to deplete SORL1 in human induced pluripotent stem cells (hiPSCs) to test the hypothesis that loss of SORL1 contributes to AD pathogenesis by leading to endosome dysfunction. We report that loss of SORL1 in hiPSC-derived neurons leads to early endosome enlargement, a cellular phenotype that is indicative of ‘traffic jams’ and is now considered a hallmark cytopathology AD. We validate defects in neuronal endosomal traffic by showing decreased localization of amyloid-precursor protein (APP) in the trans-Golgi network (TGN), and increased localization of APP in early endosomes, a site of APP cleavage by the β secretase BACE1. Microglia, immune cells of the CNS, which play a role in AD pathology also express SORL1. We therefore tested and found no effect of SORL1 depletion on endosome size or morphology in hiPSC-derived microglia, suggesting a selective effect on neuronal endosomal trafficking. Finally, because BACE1 dependent APP fragments can cause endosome enlargement, we treated SORL1 deficient hiPSC-derived neurons with BACE1 inhibitors and demonstrate that endosome enlargement occurs independent of amyloidogenic APP fragments. Collectively, these findings clarify where and how SORL1 links to AD. Moreover, our data, together with recent findings, underscores how sporadic AD pathways that regulate endosomal trafficking, and autosomal-dominant AD pathways that regulate APP cleavage, independently converge on the defining cytopathology of AD.

scholarly journals Cholesterol and Alzheimer’s Disease; From Risk Genes to Pathological Effects

2021 ◽  
Vol 13 ◽  
Author(s):  
Femke M. Feringa ◽  
Rik van der Kant
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Metabolism ◽  
Late Onset ◽  
Induced Pluripotent Stem Cell ◽  
Risk Genes ◽  
Cholesterol Levels ◽  
Technical Advances ◽  
The Central Nervous System ◽  
Induced Pluripotent

While the central nervous system compromises 2% of our body weight, it harbors up to 25% of the body’s cholesterol. Cholesterol levels in the brain are tightly regulated for physiological brain function, but mounting evidence indicates that excessive cholesterol accumulates in Alzheimer’s disease (AD), where it may drive AD-associated pathological changes. This seems especially relevant for late-onset AD, as several of the major genetic risk factors are functionally associated with cholesterol metabolism. In this review we discuss the different systems that maintain brain cholesterol metabolism in the healthy brain, and how dysregulation of these processes can lead, or contribute to, Alzheimer’s disease. We will also discuss how AD-risk genes might impact cholesterol metabolism and downstream AD pathology. Finally, we will address the major outstanding questions in the field and how recent technical advances in CRISPR/Cas9-gene editing and induced pluripotent stem cell (iPSC)-technology can aid to study these problems.

scholarly journals Up-regulation of APP endocytosis by neuronal aging drives amyloid dependent-synapse loss

2021 ◽  
Author(s):  
Tatiana Burrinha ◽  
Isak Martinsson ◽  
Ricardo Gomes ◽  
Ana Paula Terrasso ◽  
Gunnar K. Gouras ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Late Onset ◽  
Aged Mouse ◽  
App Processing ◽  
Synapse Loss ◽  
Aged Brain ◽  
Early Endosomes ◽  
Aβ Production

Neuronal aging increases the risk of late-onset Alzheimer's disease. During normal aging, synapses decline, and β-amyloid (Aβ) accumulates intraneuronally. However, little is known about the underlying cell biological mechanisms. We studied normal neuronal aging using normal aged brain and aged mouse primary neurons that accumulate lysosomal lipofuscin and show synapse loss. We identify the up-regulation of amyloid precursor protein (APP) endocytosis as a neuronal aging mechanism that potentiates APP processing and Aβ production in vitro and in vivo. The increased APP endocytosis may contribute to the observed early endosomes enlargement in the aged brain. Mechanistically, we show that clathrin-dependent APP endocytosis requires F-actin and that clathrin and endocytic F-actin increase with neuronal aging. Finally, Aβ production inhibition reverts synaptic decline in aged neurons while Aβ accumulation, promoted by endocytosis up-regulation in younger neurons, recapitulates aging-related synapse decline. Overall, we identify APP endocytosis up-regulation as a potential mechanism of neuronal aging and, thus, a novel target to prevent late-onset Alzheimer's disease.

scholarly journals Charcot-Marie-Tooth disease-linked protein SIMPLE functions with the ESCRT machinery in endosomal trafficking

2012 ◽  
Vol 199 (5) ◽  
pp. 799-816 ◽  
Author(s):  
Samuel M. Lee ◽  
Lih-Shen Chin ◽  
Lian Li
Keyword(s):  
Integral Membrane Protein ◽  
Dominant Negative ◽  
Erbb Receptors ◽  
Endosomal Trafficking ◽  
Loss Of Function ◽  
Charcot Marie Tooth ◽  
Charcot Marie Tooth Disease ◽  
Escrt Machinery ◽  
Early Endosomes ◽  
Tooth Disease

Mutations in small integral membrane protein of lysosome/late endosome (SIMPLE) cause autosomal dominant, Charcot-Marie-Tooth disease (CMT) type 1C. The cellular function of SIMPLE is unknown and the pathogenic mechanism of SIMPLE mutations remains elusive. Here, we report that SIMPLE interacted and colocalized with endosomal sorting complex required for transport (ESCRT) components STAM1, Hrs, and TSG101 on early endosomes and functioned with the ESCRT machinery in the control of endosome-to-lysosome trafficking. Our analyses revealed that SIMPLE was required for efficient recruitment of ESCRT components to endosomal membranes and for regulating endosomal trafficking and signaling attenuation of ErbB receptors. We found that the ability of SIMPLE to regulate ErbB trafficking and signaling was impaired by CMT-linked SIMPLE mutations via a loss-of-function, dominant-negative mechanism, resulting in prolonged activation of ERK1/2 signaling. Our findings indicate a function of SIMPLE as a regulator of endosomal trafficking and provide evidence linking dysregulated endosomal trafficking to CMT pathogenesis.

Response to Steroids in IQSEC2-Related Encephalopathy Presenting with Rett-Like Phenotype and Infantile Spasms

2020 ◽  
Author(s):  
Divya Nagabushana ◽  
Aparajita Chatterjee ◽  
Raghavendra Kenchaiah ◽  
Ajay Asranna ◽  
Gautham Arunachal ◽  
...  
Keyword(s):  
Late Onset ◽  
Neurodevelopmental Disorder ◽  
Epileptic Encephalopathy ◽  
Infantile Spasms ◽  
The Past ◽  
Resource Limited ◽  
The Central Nervous System ◽  
Motor Milestone ◽  
Behavior And Cognition ◽  
Atypical Rett Syndrome

Abstract Introduction IQSEC2-related encephalopathy is an X-linked childhood neurodevelopmental disorder with intellectual disability, epilepsy, and autism. This disorder is caused by a mutation in the IQSEC2 gene, the product of which plays an important role in the development of the central nervous system. Case Report We describe the symptomatology, clinical course, and management of a 17-month-old male child with a novel IQSEC2 mutation. He presented with an atypical Rett syndrome phenotype with developmental delay, autistic features, midline stereotypies, microcephaly, hypotonia and epilepsy with multiple seizure types including late-onset infantile spasms. Spasms were followed by worsening of behavior and cognition, and regression of acquired milestones. Treatment with steroids led to control of spasms and improved attention, behavior and recovery of lost motor milestone. In the past 10 months following steroid therapy, child lags in development, remains autistic with no further seizure recurrence. Conclusion IQSEC2-related encephalopathy may present with atypical Rett phenotype and childhood spasms. In resource-limited settings, steroids may be considered for spasm remission in IQSEC2-related epileptic encephalopathy.

scholarly journals The Link between VAPB Loss of Function and Amyotrophic Lateral Sclerosis

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1865
Author(s):  
Nica Borgese ◽  
Nicola Iacomino ◽  
Sara Francesca Colombo ◽  
Francesca Navone
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Motor Neurons ◽  
Adaptor Proteins ◽  
Loss Of Function ◽  
Membrane Contact Sites ◽  
Physiological Processes ◽  
Main Driver ◽  
Single Allele ◽  
Induced Pluripotent ◽  
Lateral Sclerosis

The VAP proteins are integral adaptor proteins of the endoplasmic reticulum (ER) membrane that recruit a myriad of interacting partners to the ER surface. Through these interactions, the VAPs mediate a large number of processes, notably the generation of membrane contact sites between the ER and essentially all other cellular membranes. In 2004, it was discovered that a mutation (p.P56S) in the VAPB paralogue causes a rare form of dominantly inherited familial amyotrophic lateral sclerosis (ALS8). The mutant protein is aggregation-prone, non-functional and unstable, and its expression from a single allele appears to be insufficient to support toxic gain-of-function effects within motor neurons. Instead, loss-of-function of the single wild-type allele is required for pathological effects, and VAPB haploinsufficiency may be the main driver of the disease. In this article, we review the studies on the effects of VAPB deficit in cellular and animal models. Several basic cell physiological processes are affected by downregulation or complete depletion of VAPB, impinging on phosphoinositide homeostasis, Ca2+ signalling, ion transport, neurite extension, and ER stress. In the future, the distinction between the roles of the two VAP paralogues (A and B), as well as studies on motor neurons generated from induced pluripotent stem cells (iPSC) of ALS8 patients will further elucidate the pathogenic basis of p.P56S familial ALS, as well as of other more common forms of the disease.

scholarly journals The Innate Immune System in Alzheimer’s Disease

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Allal Boutajangout ◽  
Thomas Wisniewski
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Immune System ◽  
Innate Immune System ◽  
Late Onset ◽  
Innate Immune ◽  
Amyloid Angiopathy ◽  
Functional Variant ◽  
The Central Nervous System ◽  
Congophilic Amyloid Angiopathy

Alzheimer’s disease (AD) is the leading cause for dementia in the world. It is characterized by two biochemically distinct types of protein aggregates: amyloidβ(Aβ) peptide in the forms of parenchymal amyloid plaques and congophilic amyloid angiopathy (CAA) and aggregated tau protein in the form of intraneuronal neurofibrillary tangles (NFT). Several risk factors have been discovered that are associated with AD. The most well-known genetic risk factor for late-onset AD is apolipoprotein E4 (ApoE4) (Potter and Wisniewski (2012), and Verghese et al. (2011)). Recently, it has been reported by two groups independently that a rare functional variant (R47H) of TREM2 is associated with the late-onset risk of AD. TREM2 is expressed on myeloid cells including microglia, macrophages, and dendritic cells, as well as osteoclasts. Microglia are a major part of the innate immune system in the CNS and are also involved in stimulating adaptive immunity. Microglia express several Toll-like receptors (TLRs) and are the resident macrophages of the central nervous system (CNS). In this review, we will focus on the recent advances regarding the role of TREM2, as well as the effects of TLRs 4 and 9 on AD.

Regrow or Repair: An Update on Potential Regenerative Therapies for the Kidney

2021 ◽  
pp. ASN.2021081073
Author(s):  
Melissa Little ◽  
Benjamin Humphreys
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Kidney Development ◽  
Transcriptional Analysis ◽  
Cell Recruitment ◽  
Renal Stem Cells ◽  
Induced Pluripotent ◽  
Stem Cell Populations ◽  
A Site ◽  
Regenerative Therapies

Fifteen years ago, this journal published a review outlining future options for regenerating the kidney. At that time, stem cell populations were being identified in multiple tissues, the concept of stem cell recruitment to a site of injury was of great interest, and the possibility of postnatal renal stem cells was growing in momentum. Since that time, we have seen the advent of human induced pluripotent stem cells, substantial advances in our capacity to both sequence and edit the genome, global and spatial transcriptional analysis down to the single-cell level, and a pandemic that has challenged our delivery of health care to all. This article will look back over this period of time to see how our view of kidney development, disease, repair, and regeneration has changed and envision a future for kidney regeneration and repair over the next 15 years.

FAMILIAL NONHEMOLYTIC JAUNDICE: BILIRUBINOSIS AND ENCEPHALOPATHY

PEDIATRICS ◽  
1969 ◽  
Vol 43 (3) ◽  
pp. 365-376
Author(s):  
William A. Gardner ◽  
Bruce W. Konigsmark
Keyword(s):  
Nervous System ◽  
Dentate Nucleus ◽  
Late Onset ◽  
Neuronal Loss ◽  
Bile Pigment ◽  
Histopathological Changes ◽  
Older Patient ◽  
Patient Case ◽  
The Central Nervous System ◽  
Original Report

The unique pathological findings of a case of congenital familial hyperbilirubinemia are presented. The patient (Case 3 of Crigler and Najjar's original report), although severely jaundiced, had developed normally without evidence of neurological disease until 15½ years of age. He then developed a progressive neurological deterioration which was clinically similar to infantile kernicterus. At autopsy most of his organs showed extensive intra- and extracellular deposition of bile pigment, particularly the renal papillae, atrial endocardium, intestinal mucosa, Kupffer cells of the liver, and the perivascular adventitia. Although no pigment was found in the central nervous system, there was striking neuronal loss and gliosis of the thalamus. Moderate neuronal loss was found in the putamen, caudate nucleus, dentate nucleus, and red nuclei. No histopathological changes were found in the hippocampus or cerebral cortex. It is suggested that the patient suffered from a late onset of "kernicterus" with involvement, in this older patient, of regions of the nervous system somewhat different from those in infantile kernicterus.

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